Poor compliance with aftercare treatment among dually diagnosed patients is a costly and pervasive health problem that limits the effectiveness of inpatient detoxification. Current strategies for improving compliance with aftercare treatment are minimally effective. The proposed project intends to improve current strategies by examining the impact of adding group motivational interviewing (GMI) to the standard treatment program of an inpatient psychiatric hospital for individuals with coexisting psychiatric and substance use disorders. The project aims to significantly improve compliance with aftercare treatment (e.g. AA/NA, outpatient therapy) and reduce substance use over standard inpatient treatment alone. The study specifically addresses Healthy People 2010 objectives to reduce the treatment gap for individuals with coexisting substance use and psychiatric problems and to reduce past-month use of alcohol and illicit substances by specifically targeting patient-level barriers and motivation. Ample evidence shows that motivational interviewing (MI) significantly reduces substance abuse and increases treatment engagement. As such, MI holds great promise for use in the inpatient setting and may represent a significant upgrade in the treatment services provided. However, MI is traditionally delivered one-on-one. The project seeks to demonstrate the efficacy of GMI in a group format. Until this is accomplished, MI will remain underutilized in inpatient or substance abuse treatment settings that rely on group therapy. The consequence is that motivational interviewing continues to go undelivered in inpatient settings despite the fact that this intervention may result in substantial benefits for patients, their families, and the community at large. Inpatients meeting eligibility criteria will be allocated to GMI + Standard Treatment (ST) or to ST alone using block randomization. Following admission, screening, and informed consent procedures, a group containing 5-6 participants will be invited to complete pretreatment questionnaires. Patients assigned to receive GMI + ST will be invited to return the following two days to attend two 90-minute group sessions delivered in the style of motivational interviewing. Patients receiving ST alone will be invited to return the following two days for a non-experimental group activity to control for therapist attention effects. All participants and collaterals will be contacted at a one and three month follow-up period after discharge to evaluate compliance with aftercare treatment and rate of alcohol and other drug consumption.